In many roofing applications, for example in large, flat commercial roof decks, a roofing membrane is used to seal and protect the roof deck from environmental weather conditions. The roofing membrane may be made of various materials, such as polymeric materials including EPDM (ethylene propylene diene M-rubber) or TPO (thermoplastic polyolefin). The roofing membrane is adhered overtop insulation boards or cover-boards. The insulation boards are typically secured to the roofing substrate or roof deck via an adhesive composition or mechanically fastened. Conventional adhesives used to adhere the roofing membrane to the insulations boards include mopping asphalt (typically Type III or Type IV), polychloroprene based adhesives, and polyurethane. The polyurethane adhesives are oftentimes applied directly onto the roof deck and the insulation boards are then laid onto the roof deck surface. Conventional polyurethane adhesives oftentimes include two separate parts that are mixed by an applicator just prior to being applied onto the surface of the roof deck. The two parts include an isocyanate blend and a polyol blend. Upon mixing, the isocyanate blend reacts or crosslinks with the polyol blend to form the polyurethane adhesive.
These foamed polyurethane adhesives, while effective for most substrates, have had some issues when used with fleece backed membranes, as described in U.S. Pat. No. 4,996,812, U.S. Pat. No. 6,938,386, and U.S. Pat. No. 6,742,313. Accordingly, there is room in the art for an adhesive composition in roofing applications that exhibits favorable properties, such as sufficient adhesive strength, shelf life, cure time, that also includes a renewable or environmentally favorable content that can be used with fleece backed membranes.